Research On Cascading Failure And Recovery Strategy Of Urban Public Transit Compound System

With the development of economy and urbanization,the rapid growth of urban population and the mismatch of the supply of urban public transportation resources have led to frequent urban traffic congestion.Researchers had studied and adopted various measures to the serious traffic congestion problem,among which the most effective method is to expand the performance of the urban public transportation system.Moreover,due to natural disasters such as torrential rains and earthquakes,network failures caused by technical failures of the transportation system and man-made disasters also have a serious impact on the performance of the urban transportation system,which will significantly reduce the performance of the urban transportation system and affect the social and economic production.The influence of the failure of a node in the network can spread to the entire network,that is,the phenomenon of network cascading failure occurs.Therefore,in-depth research on the cascading failure mechanism and failure recovery strategies of the transportation network is of great significance for preventing large-scale cascading failures of the transportation system and improving the performance of the transportation system.Due to their characteristics,such as large transportation capacity,low pollution,small footprint,and low price,bus and subway network have become a vital part of urban public transportation system.The urban public transportation system has a huge impact on the overall performance of the urban traffic network,and the research on its robustness has received more and more attention in recent years.However,the existing research has certain limitations,such as ignoring the topological characteristics of adjacent nodes and the destination of traffic.In most practical situations,because travelers have different destinations and the adjacent nodes are affected by the failure flow,travelers who face station failures tend to choose the travel paths of neighboring nodes with larger directional values.For example,after a subway station fails,more travelers among the exits of four subway stations tend to choose the exit with more transfer methods.Moreover,due to the difference in the passenger flow of distinct networks,the influence of the spread of failures between them is not equal,for example,the passenger flow sent per unit time of a subway station is much greater than the passenger flow sent per unit time of a bus station.Therefore,the impact of a failure in a subway station propagating to the bus network is much greater than the impact of a failure in a bus station propagating to the subway network.Hence,the urban public transportation network composed of subways and buses is described as a two-layer complex network,and the weights of the edges between layers are used to reflect the difference in the influence of failure propagation between the two public transportation methods,which can more accurately reflect the structure and functional characteristics of the public transportation system.This paper first analyzes the topological statistical characteristics of the Beijing bussubway compound network composed of the public transport network and the subway network and the interaction between the two layers of networks.Based on the existing binary influence cascading failure model,this paper proposes three cascading failure models of the urban transportation double-layer compound network that conform to the flow preferential redistribution,also compares and analyzes the results of these models with existing methods.Then,the robustness and vulnerability of the Beijing bus-subway compound transportation network by the cascading failure under random attacks and deliberate attacks are studied.The failure impact analysis of each line and node in the compound traffic network is carried out and established the evaluation system of important lines and nodes of the subway network.This work finds out that the model which considered the network topology characteristics and load influence showed the best performance in estimating the final cascade failure scale.This model can effectively improve the robustness of the urban traffic compound network.The established model and the results of this study can be applied to the cascade failure analysis of other public transportation compound systems.This research also proposes a failure recovery strategy after a cascading failure of the urban public transportation network,and analyzes the impact of different recovery strategies on the network recovery capability.Through the analysis of the cascading failure impact and failure recovery of the Beijing bus-subway compound network,the feasibility of the cascading failure model and recovery strategy constructed in this paper are verified.